Apparatus for deforming thin diaphragms



July 16, 1946. J. EVANS 2,403,915

APPARATUS EFOBMING THIN DIAHRAGMS Filed Feb. 15, 1944 Patented July 16, `1946 APPARATUS FOR DEFORMIN G THIN DIAPHRAGMS John Evans, Kingston, N. J., assigner to Radio Corporation of America, a corporation of Dela- Application February 15, 1944, Serial No. 522,527

Claims.

The present invention relates to the formation of diaphragms and more particularly to the deforming of extremely thin lms.

An object of the invention is to provide an im proved apparatus for shaping thin diaphragms or films.

Another object of the invention is to provide an improved apparatus for producing a thin dia phragm having a shape conforming to the contour of a selected shape.

A further object of the invention is to provide means for causing a thin diaphragm to vary in shape in accordance with variations of radiant energy.

Further objects will appear hereinafter.

In the accompanying drawing, Fig. i represents a sectional elevation of an apparatus embodying one form of the present invention; and Fig. 2 represents a detail embodying a modification of the invention.

Referring to the drawing, diaphragm I0 is of the extremely thin membranous type, such as may be formed by the flotation process. For example, it may be made of a cellulose derivative which is incorporated into a solution sufficiently plastic to prevent breakage and containing an ingredient to minimize the effects of humidity. Where the use contemplates a heat-responsive property, a material having a very high coefficient of expansion may be used as its base. Preferably, also, the solution is impregnated with a dye which renders the completed diaphragm opaque to heat radiation. In forming the diaphragm, an annular gasket II is mounted horizontally at the bottom of a container and completely covered with distilled Water. A few drops of the foregoing solution are deposited upon the surface of the water and the solution spreads entirely across the surface of the water in the form of a lm which is then allowed to dry su'iciently to resist movement. When thus dried, the Water level is gradually and carefully lowered so that the film seats upon the gasket I I and is then marginally affixed thereto. The film is thus framed in a substantial manner and dries completely, becoming very tight and exhibiting considerable elasticity when stretched or delformed. In the present instance, the diaphragm is coated on one side with an evaporated extremely thin layer I2 of a metallic nature forming a good conductor of electricity. In some instances, this nlm may be an aluminum coating to serve as a mirror for observation by means of an optical system.

In accordance with the present invention, the

framed diaphragm I0 is mounted in a ringy clamp I3 of insulating material fastened to the vinner walls of a hollow metal body I4 so that the dia-r phragm extends transversely thereof as indicated` in dotted lines. vided with a sight opening It', whichis coaxial with respect to the diaphragm I, while the inner face i6 of the opposite wall Il of the bod-y I4 is formed of the predetermined contour which it is desired'the diaphragm shall assume. In this instance, and by way of example, this contour is part of a sphere but may be of other 'configuration. As assembled, the diaphragm litL locates the metal layer I2 in relatively close proximity to the face I6 but spaced sufficiently therefrom as to prevent the maximum movement of the diaphragm from bringing the metal layer I2 into contact with the face I6.

For causing the desired deformation of the diaphragm, it is biased toward the face I6 by utilizing the layer I2 and the face I6 as terminals respectively of an electric circuit having a source ofvoltage I8, and conductors 20 and 2|, the conductr 2li being connected to the layer I2 and the conductor 2| being connected to the body I4. When the circuit is closed, the potential difference at the terminals I2 and I6 will bias the diaphragm I0 toward the face I6 and result in its assuming a counterpart of the selected configuration and thus serve as a datum position.

While in the foregoing the diaphragm is shaped in accordance with a predetermined contour, the invention can also be used to reproduce diaphragm deformations corresponding to variations of radiant energy. Thus, by inserting the secondary 22 of a transformer 23 in series with the circuit upon Which the voltage I8 is impressed, and including the primary 24 of the transformer 23 in a circuit having a source of electrical vibrations which have been transformed from modulated Waves of radiant energy from a heat, light or electrical source. The current of the circuit, including the terminals lf2 and I6, is thus modulated in accordance with variations of the source energy and thereby deforms the diaphragm I0 in a corresponding manner. Where the layer I2 is a mirror, these deformations can be visibly detected by a suitable optical system focussed upon the diaphragm I0 by Way of the sight opening I5.

It will noW be apparent that a novel unitary device has been devised wherein a diaphragm is caused to be deformed in a predetermined manner to conform to a selected shape or may be deformed in incremental areas in accordance with One side of the body I4 is pro-l modulations impressed upon a control voltage. The deformation o1' the diaphragm is due to the static force acting thereon by difference of potential and is effective to the end desired provided the elastic limit of the diaphragm is not exceeded. In other words, the radius of any selected curvature must be below the elastic limit of the membranous diaphragm.

Having thus described my invention, I claim:

1. In a device oi' the character stated, a hollow body having a metal wall of predetermined concave shape to form one terminal of an electrical circuit, a membranous diaphragm stretched transversely in said body in spaced relation to said wall, means associated with said diaphragm to form the second terminal of said circuit, and a source of cl'rrent in said circuit for causing a difference of potential between said terminals, whereby said diaphragm is biased to assume said predetermined shape as a datum position.

2. In a device of the character stated, a hollow body having a metal wall of predetermined concave shape to form one terminal of an electrical circuit, a membranous diaphragm stretched transversely in said body in spaced relation to said wall, a metallic lm on said diaphragm juxtaposed to said wall to form the second terminal of said circuit, and a source of current in said circuit for causing a diiference of potential between said terminals, iwhereby said diaphragm is biased to assume said predetermined shape as a datum position.

3. In a device of the character stated, a hollow body having a metal wall to form one terminal of an electrical circuit, a transparent membranous diaphragm stretched transversely in spaced relation to said wall. said body having a sight opening located on the opposite side of said diaphragm from said wall and coaxially with respect to said diaphragm, a metallic film on said diaphragm juxtaposed to said wall to form the second terminal of said circuit and also transform the diaphragm into a mirror to reflect a light beam entering said sight opening, and a source of current in said circuit for causing a diierence of potential between said terminals, whereby said diaphragm is deformed to assume a datum position.

4. In a device of the character stated, a body forming a cavity and having a metal wall to form one terminal of an electrical circuit. a membranous diaphragm mounted transversely of said cavity and substantially parallel to said wall but spaced therefrom, a metallic film on the wall side of said diaphragm to form the second terminal of said circuit, and a source of current for causing a difference of potential between said terminals whereby said diaphragm is deformed to assume a datum position.

5. In a device of the character stated, a body forming a cavity and having a metal wall to form one terminal of an electrical circuit, a membranous diaphragm mounted transversely of said cavity and substantially parallel to said Wall but spaced therefrom, a metallic lm on the wall side of said diaphragm to form the second terminal of said circuit, a source of current for causing a difference of potential lbetween said terminals to deform said diaphragm to assume a datum position, and means to modulate said current in accordance ywith radiant energy variations, whereby said diaphragm is shifted from said datum position to vary the potential difference as a function of the modulations of said means to modulate.

JOHN EVANS. 

